I would start with the original, Zeta, and the movie Char's Counterattack, in order. ZZ takes place between Zeta and Counterattack, but it's not required to understand the movie. You can take breaks...

Insurance is dirt cheap with old bikes unless it's something with a ton of collector's value, but I would caution against buying an old one. It wouldn't be so bad if you're mechanically inclined, but...